#include <stdio.h>

int main()
{
	int N, base10, lo, curr, hi, count = 0;

	scanf("%d", &N);

	/* for every digits, from lower to higher */
	for (base10 = 1; base10 <= N; base10 *= 10) {
		lo = N % base10;        /* part of the number after current digit */
		hi = N / base10 / 10;   /* part of the number before current digit */
		curr = N / base10 - hi * 10;     /* current digit */
		/* count numbers that is smaller than N and has '1' in the current digit */
		if (curr == 0)           /* count: [0~(hi-1)]1[0~9...9] */
			count += hi * base10;
		else if (curr == 1)      /* count: [0~(hi-1)]1[0~9...9] or [hi]1[0~lo] */
			count += lo + 1 + hi * base10;
		else                    /* count: [0~hi]1[0~9...9] */
			count += (hi + 1) * base10;
	}

	printf("%d\n", count);

	return 0;
}
